Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Define a pulse and a transverse wave.
• Distinguish between a pulse and a continuous wave.
• Identify the parts of a transverse wave: crest, trough, amplitude, and wavelength.
• Explain the relationship between amplitude and energy.
• Solve conceptual problems involving wave properties.

Lesson summary

This week, we begin our exploration of waves, a fundamental concept in Physical Sciences. Understanding waves is crucial because they explain so much about the world around us, from the music we listen to, to the light that allows us to see, and even how earthquakes shake the ground. In South Africa, understanding sound waves is important for sound engineering in our vibrant music industry, while understanding light waves allows us to develop better solar energy technologies to tackle our energy challenges. Further, understanding seismic waves is crucial for assessing earthquake risks in certain regions.

This week focuses on the basics: pulses and transverse waves.

Lesson notes

What is a Wave? A wave is a disturbance that transfers energy through a medium (or space) without causing any permanent change in the medium itself. Think of dropping a pebble into a still pond. The pebble disturbs the water, creating ripples that move outwards. These ripples are waves. The water itself isn't moving outwards with the ripple; it's just oscillating up and down. The energy from the impact of the pebble is what's being transferred outwards. Pulses A pulse is a single disturbance that moves through a medium. It’s a short burst of energy transfer. Imagine flicking a rope tied to a wall – the single bump you create travelling along the rope is a pulse. A lightning strike also creates a pulse of electromagnetic energy. Transverse Waves A transverse wave is a wave in which the particles of the medium vibrate perpendicular (at right angles) to the direction in which the wave is travelling. Think about shaking a rope up and down. The rope moves vertically, but the wave travels horizontally along the rope. Light waves are also transverse waves, though they don't need a medium to travel through. Parts of a Transverse Wave Let's break down the anatomy of a transverse wave: Crest: The highest point on a wave.

Trough: The lowest point on a wave.

Amplitude (A): The maximum displacement of a particle from its resting position (equilibrium position). It's the distance from the resting position to the crest or the resting position to the trough. A larger amplitude means more energy. Wavelength (λ - lambda): The distance between two successive crests or two successive troughs. It's the length of one complete wave cycle. Relationship between Amplitude and Energy The amplitude of a transverse wave is directly related to the amount of energy the wave carries. A wave with a larger amplitude carries more energy than a wave with a smaller amplitude, assuming other factors are constant. Imagine shaking a rope gently versus shaking it vigorously. The vigorous shaking produces a wave with a larger amplitude, and more energy is transferred down the rope.

Worked example

Example 1: Identifying Wave Parts

Imagine a rope stretched horizontally. You shake one end up and down, creating a transverse wave. At one instant in time, you observe a crest 0.5 meters above the resting position of the rope. You also observe a trough 0.5 meters below the resting position. The distance between two consecutive crests is 2 meters.

What is the amplitude of the wave?

What is the wavelength of the wave?

Solution:

Amplitude (A): The amplitude is the maximum displacement from the resting position. In this case, it's 0.5 meters. A = 0.5 m.

Wavelength (λ): The wavelength is the distance between two consecutive crests, which is given as 2 meters. λ = 2 m.

Example 2: Pulses on a Rope